Phthalocyanine pigment



Patented Mar. 10, 1942 PHTOGYANINE PIGMENT Maurice H. Fieysher and James Ogilvie, Buffalo,

N. 2., assignors to Allied Chemical & Dye (Jorporation, a corporation of New York No Drawing. Application April 7, 1939,

' Serial No; 266,538

(01. zoo-s14 Claims.

This invention relates .to improvements in phthalocyanine pigments and particularly in copper phthalocyanine pigments. It relates to an improved process for the treatment of the said pigments so as substantially to improve their properties, particularly for use in admixture with drying oils, as in printing inks, lithograph inks, paints, lacquers, enamels, and varnishes; and to the resulting improved pigments.

The phthalocyanines, and particularly copper phthalocyanine, are dyestuffs and pigments which have the very advantageous properties of imparting shades that are characterized by excellent fastness to light, great color strength, and brilliance.

However, in the use of these products there are certain important difiiculties which heretofore have not been successfully overcome. One of these is the tendency of the phthalocyanine pigments, and particularly copper phthalocyanine pigments, when incorporated in oil paints and inks, to inhibit the drying of the oils.- As a result, when the said pigments are used in printing or lithographic inks, the drying of the lithographic varnish is seriously retarded or prevented; so that prints made with such inks are slow to dry or do not dry at all and remain tacky and are apt to rub off or smear and to offset or transfer from the printed sheet to the contacting surface of another sheet. In some cases this inhibition of drying of the ink vehicle causes other objectionable eifects, such as striking through (penetration of the oil to the reverse side of the paper), and greasi'ness (oily halos around the prints).

In addition to this drying inhibiting property, it has been found that when phthalocyanine pigments which have been prepared in finely divided form by the usual acid pasting processes are employed as constituents of paints and printing inks,'coating films and prints of such paints and inks show a marked tendency to become dull and bronzy on drying, particularly when the paints and inks contain zinc oxide, barium sulfate and similar substrata. This bronzing effect is very undesirable.

According to the present invention it has been found that these undesirable properties can be removed from the phthalocyanine pigments by subjecting them to a mild oxidation treatment under non-acid conditions. Thus, it has been found in accordance with the present invention that phthalocyanine pigments, and especially acid-pasted copper phthalocyanine pigments, which are free from said vbronzing and from drying inhibiting effects can be obtained by treating said pigments with neutral or alkaline oxidizing agents in small amounts under mild oxidizing conditions. An especially effective alkaline oxidizing agent for acid-pasted copper phthalocyanine pigments is a dilute aqueous solution of sodium hypochlorite. This is surprising inasmuch as the phthalocyanines are attacked by strong alkali-metal hypochlorites forming conversion products soluble in alcohol, acetone and oils and resulting in phthalocyanine products of greener and duller shades which are unsuitable for the usual technical purposes.

In general, the mild oxidation treatment does not adversely. affect the brilliancy and fastness properties of the phthalocyanine pigments. Sometimes, however, the phthalocyanine pigments, especially copper phthalocyanine pigments, which have been subjected to the mild non-acid oxidation treatment exhibit a tendency,

when incorporated in lacquers or printing inks,

to produce somewhat dull, fiat and/or greenish shades on drying. This tendency is especially pronounced when the pigment lacquers or printing inks are applied to metallic surfaces, particularly of aluminum or brass.

It has been found, according to a further feature of the present invention, that the said undesirable tendency can be eliminated by giving the phthalocyanine pigment, after it has undergone the mild non-acid oxidizing treatment, a further treatment under mild reducing conditions with a mild reducing agent which is capable of reacting with the previously applied oxidizing agent to form water soluble reaction products. The pigment is thereby rendered slightly redder and more brilliant; and lacquers and printing inks in which pigments so treated are incorporated retain their brilliance on drying, and likewise have no tendency to bronze or to remain tacky. Alkali-metal bisulfites are particularly suitable mild reducing agents for the treatment of copper phthalocyanine pigments which have been treated previously with alkali-metal hypochlorites. Thus, it has been found in accordance with the present invention, when a copper phthalocyanine pigment which has been treated with sodium hypochlorite in the manner hereindescribed is subsequently treated with a dilute solution of sodium bisulfite, its shade remains reddish and brilliant even when applied in the form of a lacquer or printing composition to metallic surfaces. At the same time, the advantages resulting from the hypochlorite treatment are fully retained.

- moderate temperatures.

In the practice of the present invention in accordance with one method of procedure, a phthalocyanine pigment, preferably in a finely divided condition such as is obtainable by subjecting the pigment to an acid'pasting procedure, is treated with a neutral or alkaline oxidizing agent under conditions sufficiently mild to avoid substantial attack of the phthalocyanine. Such conditions ordinarily include the use of the oxidizing agent in a dilute condition and in small amounts relative to the amount'oi pigment,

e. g., a few percent by weight, and tothe use of In carrying out the reduction step, when employed, the reducing, agent is used under conditions which result in mild reducing action. Such conditions ordinarily include. the use of the reducing agent in a dilute condition and insmall amounts relative tothe amount of pigment, e. g.,

a few percent by weight, and to the usejof'modcrate temperatures.

The following example illustrates'the present invention. The parts are by weight.

Example 1', ,Part 1 '.350[,pa rts of copper phthalocyanine (produced, for instance, by ,con-

densingphthalonitrile with cuprous Tchloride) are dissolved in 3500 parts of 95% sulfuric acid at a temperature between 5'C. and C.-' The mixture is cooled during-the dissolutionin order tomaintain the, temperature. below '10? .Ct' The resulting solution s rownedinjz'obooparts of coldwater-and -the slurry is, diluted Wifih a further quantity of 20,000 partsof water. .The suspension which results is "filtered" and the iilter cake is washed .withwater until ireeofacidx The copper phthalocyanine press cake (about' 1950 parts) is suspended in 13,000 parts of water}- for coloring metallic surfaces. It may be further treated to convert it to a dry powder in any convenient manner; as for example in the manner set out in Example 1, Part 2.

It will be realized by those skilled in the art that the invention is not limited to the details of the foregoing examples and that changes may be made without departing from the scope of the v invention.

Thus,.the invention is notvlirnited'to the use of. sodium hypochlorite? as the oxidizing agent, since other oxidizing agents'can be used under I non-acid conditions; "as fof'exarnple, neutral oxidizing agents and 'alkaline oxidizing agents. As ,neutral oxidizing agentsthere may be men- 7 tioned hydrogen peroxidejjpotassium "persulfate,

alkali-metal ,riitrites and alkali-metal perman- V ganates. ,As' alkaline oxidizing agents there may be mentioned sodiump jroxidaanmms solutions ethane alkaline ofnhydrog'enfperoxide, mans-n M her hypohalites;

earth metal hypochlorite" .While'the neutralioxidizin agents improve the oil' drying 'properties' of, I the pigments and elimi-' nate bronzing, the pigments treated with "such neutral-oxidizing agentsare not as brilliant inpaint films andprints' as the pigments which have been treated ,withalkaline oxidizing agents. Hence, for the treatment of pigments which are to be used. inthe making of paints, printing inks and the like,' alkaline oxidizing agents are preferred.

In carrying out the-"oxidation treatment, the

oxidizing agent is "employed under conditions resulting in only a mild oxidizing action. In order to secure such conditions, the pigment-is :preferably slurriedor suspendedin a largeamount of.

- ilw'aten and the slurry" is. .treatedr withxa vsmall and the slurry is heated to about 60 C. Then-" 65parts of am per'cent's'odium hypochlorite solution (which has been prepared by dissolving 125 partsfof sodium hydroxide in 7'75 parts of' water, and passing in 100 parts of chlorine while cooling to maintain the temperature between 0 C. and 5? C.) are added slowly. After agitating at about 60 C. for 1 hour, the temperature is raised to about 80 C. in order to decompose theexcesszsodium hypochlorite. The slurry is' then filtered; .the. filtercakeis washed thoroughly -zwith hot waterpan'd sucked 1dry."---=.

Part waterpastefmay be prepared from amount of theoxidizingfageht Ineiiect this is atreatment with a highly dilute solution of the oxidizing agent. :Preferably the oxidationv treat nient is carried out at temperatures above or'dinary atmospherictemperature, e. g.-, above 25 C.,

in order "to-:accelerate'=athe treatment; but high temperatures are avoided in order-"to. maintain mild oxidizing conditions and, when employing hypohalites, to avoid their decomposition.v

' ,Thus, in carryingout' the process described in the press'cake ofthe treated pigment by addition of a small quantityof dispersing agent (e. g., 0.05

' per cent to 2 per cent-of Leukanol), and standardization of the paste to the desired strength in the usual manner.---Th'e pigment may be prepared in powder form by drying the press cake in enamel pans at- 90to 100 C., with or without the addition of dispersing agents, protective agents, etc., and grinding to the desired degree otfineness. The pigment is substantially unaltered in shade as a result of the hypochlorite treatment.

When used with lithographic varnish in printing inks, it does not retard or prevent drying of the varnish. It yields paints and printing inks which do not become bronzy on drying,- even when used in admixture with zinc oxide or barium sulfate.

Example 2.--The product of Example 1, Part 1, while still'in the filter as filter cake, is treated by circulating approximately 20,000 parts of aqueous sodium bisulfite solution of about 1 per cent concentration through the cake in the filter. The pigment is then washed with hot water until substantially free of salts, and again sucked dry. The resulting pigment is specially suited I the-foregoing 'examples,'ithe:pi'gment may 'be susper 10,000 partspf solution by weight (0.02 to I 0.10 per cent concentration). The other oxidizingagent's may be employed in equivalent quantities.

In carrying out the process of the foregoing Example 1, the temperature of the oxidizing treatment bath is preferably maintained above 50 C., and, in order to avoid the rapid decomposition of the sodium hypochlorite solutions by excessive heat, the temperature is preferably maintained below (3., a treatment for about 1 hour at 60 C. ordinarily being suflicient. With more stable oxidizing agents, for example potassium persuliate, higher temperatures may be employed; e. g., C.

In carrying out the reducing treatment, the mildly oxidized pigment may be treated with the of the mildly I the '1 with an aqueous solution of sodium bisulfite in ployed is preferably weight per part of dry pigment. The treatment is preferably applied at ordinary atmospheric temperatures, e. g., from 10 action to the reduction of f jstances.

nor to the treatment with the invention;

,brominated and highly chlorinated phthalo- -cy"a'nines, which are generally green pigments. The process of the present invention is especially I applicable to the treatment of. copper'phthalo-,

. ,The igment. is treated in form, and

. and dyes, such as vatdyes.

phoric acid, ethyl sulfuric phthalocyanine pigment reducing agent in any convenient manner; e. g.. by slurrying or suspending ,it in an aqueous solution of the reducing agent. A simple and effective procedure is to circulate the reducing solution through the filterin which the pigment is held as a press cake resulting from filtration oxidized pigment.

press cake of pigment obtained after mild oxidation treatment may be washed Thus the such an amount that from about 2 to about 100 parts by weight of sodium bisulfite are employed per 100 parts by weight of dry pigment, the concentration of the sodium bisulfite solution not exceeding 1 per cent by weight, and preferably being from about'0.l per cent to about 1 per cent .by weight. The total quantity of solution emnot less than 15 parts by C. to 30 C. Higher order to limit the reeasily reducible subtemperatures are avoided in 1 The invention is not limited to the use of "[sodium bisulfite as the reducing agent in the mild Qfreduction step.. Equivalent amounts of other I mild reducing agents which react with. the

previously applied oxidizing soluble products, but which are not sufficiently agent to form waterper phthalocyanine Weclaim:

1. A process .ofimproving an 801d pasted copper phthalocyanine pigment which comprises subjecting said acid pasted pigment to a mild oxidation treatment. with a dilute aqueous solution of an inorganic acid conditions.

2. A process of improving an acid pasted coppigment which comprises subjecting said acid pasted pigment to theoxioxidizing conditions.

3. A process of improving an acid pasted copper phthalocyanine pigment which comprises subjecting said acid pasted pigment to the oxidizing action of'a dilute aqueous solution of an alkali-metal hypochlorite under mild oxidizing an aqueous solution reactive to attack the phthalocyanine molecule ;under the, conditions of treatment, may be used.

Suitable reducing agents are, for instance, alkali-metal arsenites, ferrocyanides, neutral sulfites, etc.

The invention further is not limited to the treatment of specific phthalocyanine pigments of pigments produced by any special procedure. Thus, various phthalocyanine pigments may be treated in accordance as for example, highly cyanine pigments.

a finely divided preferably in the. form resulting from The acid pasting of the pigment skilled in the manufacture of insoluble pigments the mixture not higher than 30 C. and preferably between 5 and 10 C.

In drowning the resulting solution, an amount of water from about 6 to about 10 times the weight of the sulfuric acid solution may be used, and the water may be cold or hot. For ordinary pigments, water at a temperature of about 10 to 30 C. may be used for drowning the solution. For the production of a more finely divided pigment particularly adapted for the manufacture of powders, it is desirable, however, to preheat the water to about 80 C. or higher before adding the sulfuric acid solution thereto.

subjectingsaid acid to a mild reduction v conditions.

4. A process of improving an acid pasted copper phthalocyanine pigment which comprises treating said acid pasted pigment with a small amount of sodium hypochlorite in the form of of not more than about 0.10 per cent concentration at a temperature above 25 C. and below 80 C.

5. A process of improving an acid pasted copper phthalocyanine pigment which comprises forming a slurry of said acid pasted pigment in 20 to 50 times its weight of water, mixing with the resulting slurry sodium hypochlorite in an amount equal to a few per cent of the weight 10f saidpigment, and heating the mixture at a Y temperature of about 60 C.

6. A process of improving an acid pastedcopper, phthalocyanine pigment which comprises pasted pigment to a mild oxidation treatment with a dilute aqueous solution of an inorganic'oxidizing agent under nonacidconditions and then subjecting said pigment reducing agent.

. 7. A process of improving a phthalocyanine pigment which comprises subjecting an acid pasted phthalocyanine pigment to the oxidizing ac tion of a dilute aqueous solution of an alkaline inorganic oxidizing agent under mild oxidizing qconditions, and then subjecting said pigment to l a reducing treatment under mild reducing conditions with an inorganic reducing agent capableof reacting with said alkaline oxidizing agent to form a water-soluble product.

8. A process of improving an acid pasted phthalocyanine pigment which comprises treating said pigment with a small amount of an alkali metal hypochlorite agent in the form of an aqueous solution of not more than about 0.10

per cent concentration under mild oxidizing conditions, and then treating said pigment with a sulfite of an alkali metal in the form of an aqueous solution of not more than about 1 per cent concentration under mild reducing conditions.

9. A process of improving an acid pasted phthalocyanine pigment which comprises treating said pigment with an aqueous solution of sodium hypochlorite of not more than about 0.10

per cent concentration in such an amount that not more than about 2 parts of sodium hypochiorite is present the pigment, at a temperature above 25 C.

and below C., and then treating the said pigment with an aqueous solution of sodium blsulflte of not more than 1 per cent concentration in such an amount parts of sodium that there is present 2 to bisulfite per 100 parts by oxidizing agentunder non-f treatment with an inorganic per 100 parts by weight of below 80 C. and then treating said pigment with at least 15 parts 01 an aqueous sodium bisulflte solution of not more than about 1 per cent concentration at a temperature between 10 C. -and MAURICE H. FLEYSHER. JAMES OGILVIE. 

